The persistence of musculoskeletal pain after an acute injury, or in the presence of repetitive trauma, is common and debilitating. Inflammation of tissues is an important factor in the pathophysiology of acute and chronic overuse injuries, and there is growing concern that the use of NSAIDs may retard the full healing of tissues in addition to causing frequent and potentially serious side effects. It is therefore important to understand and develop treatments that may activate naturally occurring mechanisms to enhance the healing of injuries and prevent chronic musculoskeletal pain without the use of drugs. It was recently shown that the resolution of inflammation involves specialized pro-resolving mediators (SPMs) derived in part from dietary n-3 fatty acids, and our previous studies have begun to show a link between stretching of connective tissue and local resolution of inflammation. In rodent models, daily stretching for 10 minutes decreased both acute and chronic inflammation and increased local levels of SPMs in the inflammatory lesion. Furthermore, stretching of connective tissue ex vivo decreased the migration of neutrophils and enhanced the tissue concentration of SPMs, suggesting that stretching has direct pro-resolution effects within connective tissue. In this project, we propose a series of experiments testing the hypotheses that: 1) stretching of connective tissue promotes a local eicosanoid shift from pro-inflammation (leukotrietenes) to pro-resolution (resolvins, lipoxins), reduces neutrophil accumulation and enhances the production of pro-resolution macrophages; 2) both NSAIDs and a diet deficient in n-3 fatty acids decrease stretch-induced SPM production and inhibit the effect of stretching on the natural resolution of inflammation and 3) stretching has direct pro-resolution effects within connective tissue that involve fibroblast-matrix interaction mechanisms. We will test these hypotheses using in vivo rodent models of acute self-limiting and chronic subcutaneous inflammation, an ex vivo model of neutrophil migration and in vitro fibroblast- and monocyte-populated collagen gels. Investigating the effect of stretching on inflammation resolution is significant because of the current limitations and side effects of pharmacological approaches to treat musculoskeletal pain and inflammation. Our study is innovative in its investigation of novel mechanisms linking connective tissue, body movement and immune responses. If successful, this project will significantly impact the understanding of fundamental, naturally occurring healing mechanisms relevant to pharmacotherapy, diet and a range of movement-based therapies with a stretching component including physical therapy, Tai Chi and yoga.